Implants are used for therapy of bone fractures, for example, in the form of nails, screws, or plates. Fundamentally, the process that occurs in the body when the broken ends of bones grow together is supposed to proceed with as little disruption as possible and in regular anatomical manner. In this connection, the most usual method is the use of an immobilization bandage in the form of a plaster or plastic cuff. This is generally used for uncomplicated fractures. The disadvantage of this method is the long loss of function of the injured extremity, leading to muscle and bone degeneration (atrophy) if the period of non-use is a long one.
In order to prevent atrophy, and in order to be able to begin rehabilitation as early as possible, it is increasingly true that an operation is carried out in the case of bone fractures wherein more precise restoration of the anatomy and better fixation of the fragments are possible using nails, screws, or plates. For older patients, this is often the only possibility so that the patients do not lose their previous independence for a long period of time or even permanently.
Usually, such functional implants for support, fixation, and hold are produced from non-degradable materials, such as medical steel or titanium (alloys). After the bone fragments have grown together, these implants remain in the body or they are explanted during the course of another operation.
Functional implants that remain in the body can lead to irritations, such as inflammations, in the long term. Explantation of the implant leads to another avoidable operation.
In order to provide a remedy here, orthopedic implants are known, for example, from U.S. Patent Publication No. 2008/0015578, which are produced at least in part from metal materials that can be degraded by the body of the implant wearer. Metals, such as iron, magnesium, zinc, tungsten, as well as mixtures or alloys of these, are used.
An active orthopedic implant, for example, in the form of a bone plate, is known from U.S. Patent Publication No. 2006/0052782, which has at least one microchip and a sensor connected with it. The sensor responds to physical signals from the implant or from the patient tissue, such as temperature, pressure, or tensile stress, for example. The data recorded by the sensor are processed by the microchip and transmitted to a receiver disposed outside of the patient, such as a personal computer, for example. In this way, the medical care personnel can undertake a diagnosis, for example, of the effective period of functioning of the implant, the stress on the bone plate, and possible complications that can occur in the case of orthopedic implants, in the form of infections, non-healing of the fracture, and fatigue. Furthermore, the implant can have electrodes on its surface to support the healing process of the bone fracture.
A disadvantage of functional implants composed of a degradable material is the fact that the degradation process is dependent on the conditions in the body of the implant wearer, in each instance. In particular, the degradation process cannot be actively influenced.